1. Field of the Invention
The invention generally relates to light-sensing guidance systems for aircraft, and more particularly to a sun-sensing guidance system particularly suited for use aboard high-altitude unmanned aircraft and employed for constantly providing heading signals for maintaining the aircraft's track on a selected course line.
2. Description of the Prior Art
The prior art is, of course, replete with light-sensitive guidance systems for unmanned aircraft and the like. For example, U.S. Pat. No. 2,155,402 discloses a sun compass having a pair of normally balanced photo-electric, heat, or other radiation sensing circuits. The sensitive elements of the radiation sensing circuits are so arranged that when the device bears a predetermined angular relation to a source of celestial radiant energy, such as the sun, the circuit achieves a balanced condition and an angular relation in terms of two geographical directions becomes known.
U.S. Pat. No. 2,921,757 discloses a long-range navigation device installed in aircraft, or guided missles, which serves to orient an aircraft in accordance with a selected course relative to a celestial body. A simulated track is plotted as a function of time and a calibrated direction of the celestial body; the device is linked with a track so that a compass will continuously realign the track relative to the aircraft in accordance with the instantaneous position of the celestial body.
U.S. Pat. No. 2,182,717 discloses a motor-controlled system for a rudder which utilizes light sensitive devices for controlling the motor comprising a reflector mounted on a compass card, the position of which is changed in response to changes in the direction of deviation from a selected course, with a resultant light signal being picked-up for providing an error signal employed in reorienting the craft's rudder.
U.S. Pat. No. 3,423,047 discloses an apparatus which employs a light sensitive device for stabilizing the position of flight for a flying body utilizing restoration means dependent upon whether the deviation occurs in a small range, or in a large range outside the small range. A first restoring action is initiated responsive to deviation in the small range, and if the deviation progresses into a large range, a second restoration is initiated. A control circuit having photo sensing devices responsive to changes in position of light-beams impinging thereon serves to provide the necessary output signals.
In other words, it is recognized that numerous attempts have been made to utilize light detection devices for providing directional intelligence in navigational systems. Unfortunately, use of prior art devices and systems heretofore made available in the industry, tends to be impaired by one or more inherent inadequacies. For example, an on-board guidance system must be dependable, preferably of light-weight construction characterized by simple circuitry, and be economically feasible to fabricate and maintain. The desirability of these characteristics is particularly significant in instances where the craft within which the system is to be employed is one particularly designed for high-altitude, unmanned surveillance missions and having contemplated single mission longevity.
It is, therefore, the general purpose of the instant invention to provide a simple, economic, light-weight and dependable sun-sensing guidance system for high-altitude, unmanned aircraft.